1. Field of the Invention
The present invention relates to an image exposure apparatus which is switchable between a reader state in which an image is projected on a screen for observation and a scan state in which the image is subjected to scanning exposure.
2. Related Background Art
In such field there is already known a microfilm reader-printer, which has a reader function for magnified projection of an image of a microfilm on a screen for direct observation, and a print function for producing a reproduced print of the image. FIGS. 11 and 12 are schematic views of an example of such reader-printer, respectively in the reader mode and in the print mode.
A film illuminating unit is comprised of an illuminating lamp 1 and a condensing lens 2, and a desired image frame of a microfilm F is retrieved and positioned at a film illuminating position above said condensing lens 2.
The light transmitted by the film F enters a projection lens 3 and, in the reader mode shown in FIG. 11, the light transmitted by the projection lens 3 is guided by a first reader mirror 14 and a second reader mirror 15 to the internal face of a reader screen 13, provided at the front portion of the apparatus, whereby the image information of the image frame of the microfilm, placed at the film illuminating position, is projected in magnified manner onto said screen 13 and said magnified projected image can be observed from the external side of the screen 13. The first reader mirror 14 of the reader system is provided at the top side of the apparatus while the second reader mirror 15 is provided at the rear side of the apparatus, so that a 4-shaped reader optical path is formed when seen from the left side of the apparatus.
First and second scanning mirrors 5, 6 are supported by a common scanning case 100, with a predetermined mutual distance and in respectively downward positions inclined by 45.degree. in such a manner that the extensions of the reflecting faces mutually cross perpendicularly.
Said scanning case 100 can reciprocate in the horizontal direction, as indicated by an arrow d-b, along a guide member and under the function of drive means controlled by control means (not shown). The first and second reader mirrors 14, 15 and the screen 13 are positioned outside the moving path of the scanning case 100.
In the reader mode, said scanning case 100 is moved in the forward direction b to a right-hand end point in the apparatus and remains in a reader position (home position) at the right-hand side of the apparatus, outside the optical path (reader optical path) between the projection lens 3 and the first reader mirror 14 of the reader system, as shown in FIG. 11.
A print mechanism 16 provided in the lower part of the apparatus is comprised, in this example, of a transfer electrophotographic copying mechanism. There is provided a rotating electrophotographic photosensitive drum 4, around which are provided already known image forming process means such as a charger, a developing unit, a transfer unit and a cleaning unit (said means being omitted from the illustration). There are also provided a sheet cassette 10, copy sheets 9 stacked on said cassette 10, a sheet guide member 17, paired transport rollers 18, 19 and a sheet discharge tray 11.
When a copy button (not shown) is depressed in the reader mode shown in FIG. 11, the control system of the apparatus is switched to the print mode to activate the print mechanism 16 thereby clockwise rotating the photosensitive drum 4 with a predetermined process (peripheral) speed. Also the scanning case 100 effects a forward movement (back scan) d from the reader position to the left, with a predetermined controlled speed. As a result of said forward movement d of the scanning case 100, the first scanning mirror 5 enters and moves, as shown in FIG. 12, in the reader optical path between projection lens 3 and the first reader mirror 14 of the reader system. The second scanning mirror 16 is positioned above the photosensitive drum 4 of the print mechanism 16.
After the forward movement d of the scanning case 100 by a predetermined distance, it is shifted to a reverse movement b to the right, and the reversing speed of said scanning case 100 is controlled at 1/2 of the peripheral speed of the photosensitive drum 4 of the print mechanism 16.
By said reversing movement b of the scanning case 100, the above-mentioned reader optical path is scanned by the first scanning mirror 5, and the scanned light is reflected by the first and second scanning mirrors 5, 6 and irradiates, as a slit, the rotary photosensitive drum 4 (image exposure), whereby the print mechanism 16 forms an enlarged print of the image information of the image frame of the microfilm F. After the completion of image exposure on the photosensitive drum 4, the scanning case 100 continues the reverse movement b to the original reader position, whereupon the apparatus returns to the reader mode.
The length of the reader optical path from the projection lens 4 through the first and second reader mirrors 14, 15 to the screen 13 in the reader mode is the same as that of the scanning optical path from the projection lens 3 through the first and second scanning mirrors 5, 6 to the exposed portion of the photosensitive drum 4.
In most of the apparatus of the above-explained kind, the reproduced print is obtained by the known electrophotographic process utilizing slit exposure on a photosensitive drum as explained in the foregoing example, but for responding to the recent requirements for diversified functions in such apparatus, there is often added a function of reading the image information by the use of an image pick-up device such as CCD in addition to the photosensitive drum 4. There are also known apparatus capable, based on the read image information, of effecting AE (automatic image density control) or image processing such as black frame erasing at the formation of reproduction print by the photosensitive drum 4, and of recording the read image information for example in a magnetooptical disk.
In such apparatus, there is also known the simplification of the configuration by utilizing the scanning optical path for the aforementioned reproduction print, also in the reading of the image information. More specifically, as shown in FIGS. 11 and 12, a rocking mirror 101 for switching the optical path is provided immediately in front of the exposure portion of the photosensitive drum 4 and the image is focused on a one-dimensional photosensor array positioned on thus branched optical path, whereby the image information can be read.
In such case, the length of the optical path from the projection lens 3 through the first and second scanning mirrors 5, 6 and the rocking mirror 101 to the photosensor array 12 is the same as that of the reader optical path in the aforementioned reader mode or that of the scanning optical path in the aforementioned print mode. Such optical path branching by the rocking mirror 101 allows a sharp focused image to be obtained on the photosensor array 12, as in the aforementioned reproduction printing.
However, in the conventional configuration as shown in FIGS. 11 and 12, the apparatus becomes inevitably bulky because, in the reader mode, the relatively large scanning case 100 supporting the first and second scanning mirrors 5, 6 has to be retracted from the reader optical path by the rightward movement in the apparatus as shown in FIG. 11 and a large escape space has to be secured for this purpose. Also in case the function for reading the image information is provided by the photosensor array 12, the apparatus becomes bulky and expensive in cost because there are required the rocking mirror 101 for optical path branching and a driving mechanism for said rocking mirror.